Pressure Post-Processing Pressure Post-Processing

The commands discussed in this section deal with the frequency response of the pressure on a panel. As mentioned previously, the data for these commands depends on the manner in which the original frequency response data was computed. If it was computed with an RAO command, then all options and data discussed here are available. If it was computed with an SRESPONSE command, then no environmental data can be specified.

To obtain the frequency response of the average pressure over a panel, issue the command:


     FR_PANPRESS, :PAN_SEL   -OPTIONS

Here, :PAN_SEL is a selector for the panels you want pressure on, and the only available option is -FILE. If one uses this option, the pressures on panels selected by :PAN_SEL will be written to the ppo file, and the Disposition Menu will not be entered. Alternatively, if the option is not used, :PAN_SEL should select only a single panel, and the user is placed in the Disposition Menu to dispose of the results as desired.

To compute statistics of pressures in irregular seas, one should issue:


     ST_PANPRESS, :PAN_SEL, ENV_NAME, -OPTIONS

where the available options are:


     -SEA, SEA_NAME, THET, HS, PERIOD, GAMMA

     -SP_TYPE, TYPE

     -SPREAD, EXP

     -E_PERIOD, EP(1), EP(2), .....

     -CSTEEP, YES/NO

Here, the statistic of the pressure on panels selected by :PAN_SEL will be returned and the user will be placed in the Disposition Menu. Here, there is no limit on the number of panels selected, and the statistical result is the statistic specified with the last -PROBABILITY option on a &DEFAULT command, and If the original response data was produced with the SRESPONSE command, then no additional sea data can be specified.

The remainder of the options have a similar syntax to those of the &ENV command. In fact, commands using these options not only initiate the computation of quantities in an irregular sea, but is also an &ENV command. Thus, when one issues one of this command with a non-blank ENV_NAME, he is altering the definition of this environment within the database. If ENV_NAME is omitted, then the environment used will be totally defined by the options specified. The options -SEA, -SPREAD and -SP_TYPE are used to define the sea state to which the vessel will be subjected. The -E_PERIOD option can be used to generate results for seas of several different periods. If this option is omitted, then a single period of PERIOD will be considered. With the option, periods of PERIOD, EP(1), EP(2), ... will be produced. If -CSTEEP is specified with a YES/NO of YES, then the height of the wave will be altered so that all seastates have the same steepness as the initial one. Otherwise, the wave height will remain constant.